Well, you could always send Bob an email, and ask him to send you a list of all of the exact components he uses and where to get them (which probably wouldn't be very polite), or, failing that, you could do your own research and figure it out. Or, better yet, you could purchase an upgrade kit from Bob, which includes the components that are recommended to be replaced, and which is less expensive than purchasing an entire new set of crossovers.
http://www.critesspeakers.com/prices-crossover_repair_kit.html